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This is how to fight slippery roads

Published Oct 19, 2010

This is all about a measurement system which can be used to detect and warn of icing on our roads. So-called black-ice is of particular interest, i.e. ice that is not visible to the naked eye but which produces extreme slipperiness. KTH researcher Mats Riehm’s initiative will lead to safer winter roads but also very large cost savings for winter road maintenance along with positive environmental benefits.

Mats Riehm
Mats Riehm, PhD student at KTH

Between 200,000-300,000 tonnes per year, this is how much road salt is spread on our roads each year. The cost of this and other winter road maintenance in Sweden amounts to approximately SEK 2 billion annually, according to recent figures from the Transport Administration.

“The measurement system can lead to very significant cost savings as it will streamline winter road maintenance ," says Mats Riehm, PhD student at the Department of Land and Water Technology in the ABE School at KTH.

In short, his idea is based on the setting up of infrared thermometers and infrared cameras at the approx. 700 weather stations located throughout Sweden. Infrared thermometry, a technique that has fallen in price dramatically in recent years, reads the energy released when the surface freezes. Together with small cooling elements in the road surfaces which test freeze the road and in combination with calculations, it is possible to see how much salt is left and therefore when it is time to add salt again. The roads therefore will not need as much salt as before, i.e. we will no longer be in the dark and without reliable information as to whether the salt is really needed.

“The measurement system will mean that it will be possible to see how likely ice will develop on a road over the next few hours. It is very helpful for those who are in charge of road maintenance if they know this. It is about using the right amount of salt at the right time and in the right place," says Mats Riehm.

If more salt is needed and spread on a road, it will provide safer roads. If less salt is needed and is not spread, it means less corrosion on cars, but above all it provides a great service to the national economy and the environment.

“The harmful effects of road salt on groundwater and vegetation is well studied and documented," says Mats Riehm.

The technology he has developed has just been patented, and a company called MetSense has been started together with colleagues at Gothenburg University. What now remains is to make exhaustive tests of the technology during the coming season, which began last winter.

“The market potential is considerable. The technology is relevant in Europe, but also in China, Japan, Canada and the United States. Worldwide, for example, there are 8,000 road stations where the technology could be readily assembled," says Mats Riehm.

For more information, contact Professor Mats Riehm at 08-790 79 44 or

Peter Larsson

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Last changed: Oct 19, 2010